Decorative and protective coatings deposited by physical vapor deposition (PVD) have in recent years become important in the fields of plumbing hardware and accessories, home hardware such as doorknobs and hinges, automotive parts, and many other applications. The most commercially successful of these coatings have been those possessing a brass or gold color, which coatings generally consist of the nitrides of metals or metal alloys such as zirconium nitride, titanium nitride, and zirconium-titanium nitride. It is known to produce coatings with colors similar to those of pure copper and copper alloys (e.g. bronze) by using the carbonitrides of such metals and alloys rather than simple nitride compounds. It is difficult, however, using these materials, to produce a coating having a color closely matching that of pure copper.
Another problem with known carbonitride coatings is that their resistance to common household chemicals and to salt-spray testing is generally inferior to that of simple nitride PVD coatings. As a result, carbonitride coatings tend to tarnish more readily in service.
Yet another problem with carbonitride coatings concerns the stability and repeatability of coating deposition processes, which are adversely affected by the carbon-containing gases used to form the carbonitride compounds.
Accordingly, it would be desirable to provide vapor deposited coatings which have a color very similar to that of pure copper or other desirable metal coatings, but which have substantially better resistance to chemicals and tarnishing than copper itself and also to conventional metal carbonitrides. It would further be desirable to provide coatings having a controllable range of colors similar to those of copper and copper alloys such as bronze, and also to other colors such as, for example, pinkish and reddish shades of brass, gold, chrome, gray. It would also be desirable to provide a coating method which is stable and repeatable and which does not necessitate excessive equipment maintenance.
It would be desirable to provide a coating and/or method that provides one or more of these or other advantageous features. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments which fall within the scope of the appended claims, regardless of whether they accomplish one or more of the above-mentioned needs.